> Of course the old ban on hyphenating st and ck was due to the use of lead
> ligatures of st and ck in Fraktur typography. One presumes that such rules
> must continue to apply in modern German written in Fraktur.

I guess that explains the old Schiffahrt/Schiff-fahrt rule as well:
Printers didn't have an fff ligature, and an ff ligature followed by a
single f is pretty ugly.

And they were serious about not separating ck and st --- even in
spatiated text. "Versteckt" would come out as "V e r st e ck t".